Upsizing to too big a bar and chain will make the chain not work
optimally, bogging the motor down even further. 38cc wont have the
power to handle a 20 inch bar (which will also probably have a much
deeper, more aggressive chain). It will probably run, and make the
chain go, but I doubt you'd make very much progress actually cutting -
very slow going. Also, a larger bar/chain will probably mean a
*thicker* chain which won't fit around your clutch. I just went
through this with my Husqvarna. Replacing the clutch would have worked
within reason (there's only so much room in there for the clutch), but
at that point I was more than halfway to just buying a bigger saw that
was built for what I needed.

On Jul 25, 11:29 am, yddraig wrote:
Are there any problems when replacing a chainsaw bar say from 16
inches to 20 inches? I have a PoulanPro 3800 series and would like to
add a larger bar (occasionally) to cut larger logs. Poulan says that
the saw was not designed for a 20 inch bar (of course they do), am I
doing anything inherently risky by upsizing?

Thanks